Detonator assemblies comprising an electrical or an electronic detonator connected via lead wires to a harness are known in the art. In use, a plurality of such assemblies are connected via the harness to a blast controller and located in respective blast holes of a blast site. The blast controller is used to control the detonators and to cause them to detonate in a particular sequence and pattern, to cause a desired multi-shot blast pattern.
Due to certain reliability problems with the detonator assemblies, it is the practice in some countries to place in each blast hole a first detonator assembly as well as a second, parallel or back-up detonator assembly. It will be appreciated that the provision and connecting of a separate, parallel back-up detonator assembly not only take up unnecessary time, but are cumbersome and errors may occur in the connection of the back-up assembly.